Insulator.



R. H. MARVIN.

INSULATOR.

APPLICATION FILED MAYH. 1916.

Patented Nov. 6, 1917.

3 SHEETSSHEETI 5 wvewto c Hovnu s R. H. MARVIN.

Patented Nov. 6, 1917.

3 SHEETSSHEET 2.

ftozuuys R H. MARVIN.

INSULATOR. APPLICATION FILED MAY H. 1916.

1 245,940. Patented Nov. 6, 1917.

3 SHEETSSHEET 3- a vwewtoz UNITED STATES PATENT onnionl RICHARD H. iunvm, or EAST nrvnitroon, onro, Assrenon, 'ro rnn n. mourns SONS COM AN F E ST LIVER/13001 OHl A COBPOR TION OF OHIO.

INSULATOR.

Specification of Letters Patent.

I Patented Nov. 6, 1917.

Application fi ed May 11, 1916. Serial No. 96,832.

To all whom it may concern:

Be it known that I, RICHARD H. MARVIN, a citizen of the United States of America, and residing at East Liverpool, in the county of Columbiana and State of Ohio, have invented a certain new and useful Improvement in Insulators, of which the following is a specification.

My invention relates to insulators and particularly to insulators of the multiunit type, andthe object of my invention is to provide an insulator in which the units are graded to insure a more even voltage distribution than has heretofore been attained.

In the accompanying drawings,

Figure 1 is an elevation, in partial section, of a multiunit suspension insulator in which my invention is embodied in one form;

' Figs. 2, 3 and 4 are elevations, half in section, of the three graded units employed in the insulator shown in Fig. 1, but drawn to a larger scale;

Fig. 5 is a diagram of a suspension insulator with graphic indications of three principal elements of capacity which must be taken into consideration in grading an insulator;

Fig. 6 is a diagram showing the distribution of voltage over a string of ungraded insulators; and

Fig. 7 is a diagram of the distribution of voltage over a string of insulators graded in accordance with my invention.

The uneven distribution of voltage along a string of suspension insulators is well known. With a small number of units this feature is not serious and scarcely justifies the complication and expense required to overcome it. But with an increasing number of units, the distribution becomes increasingly poorer, and a limit is soon reached where additional units add very little to the value of the string. With the increase .of operating voltages the problem of meeting this phenomenon becomes serious.

In general the unit next to the line has the largest proportion of voltage across it, the ,succeedingunits taking -a smaller and smaller amount. fi'lhis "condition is unsatisfactory for two reasons, viz., the units near the line have to stand an excessive strain, while the units near the tower or grounded end of the string have alower voltage acrcxss them than is desirable for efiicient service.

The present construction afi'ords simple means by which a more even distribution of .the voltage across all the'units of the insu- The capacity (C) between the metal fittings on one portion of the string to those on any other portion, and (4) the capacity (not indicated) between the metal fittings and the line wire. Usually only the first two groups are considered, but experiments have indicated that the others have an appreciable effect.

It is readily seen (Fig. 5) that the current to charge all the capacities C C C must pass through the capacity C of unit No. 1. The capacity C of unit No. 2 has to supply current to the following C capacities but has a smaller number'of C and C capacities to charge. Consequentlythe first unit has a higher voltage across it than the second, and so on. It appears therefore that if we neglect the C capacities, unit No. 7, viz., the grounded unit,

AND

will have the lowest voltage across it. The

capacities C tend however to make the voltage across the middle unit the lowest, so that the total result is that one of the units near the grounded end, and not the grounded unit, has the lowest voltage across it. This is indicated in Fig. 6 subsequently referred to.

The principle of grading fore in varying the capacities C from unit to unit, so that the voltage across each unit is kept as nearly as possible the same. This means that the unit next .to the line must have the greatest C capacity and successive units, decreasing amounts. While this is theoretically the most perfect method since it secures the most perfectly even distributionof voltage, it entails great compliconsists theregroups.

In the illustrative embodiment of my in: vention here indicated, I'have shown a suspension insulator 10. having fifteen units,

divided into three groups a, b and a. Each insulator unit is of well known general type having an inverted cup-shaped head 11, outstanding skirt 12, with petticoats 13 dependingtherefro'm. A metallic cap 14 secured by ceihent 15 to each head, has a perforated split boss 16 between the sides of which enters the downwardly extending perforated shank '17 of the pin 18 cemented within the head 11 and secured to the'boss 16 by a cross pin 18. A

' In order to increase the capacity of the insulators in group a I provide the same with an increased metal area above and below the insulator skirt and adjacent cap 1% and pin 18. This metallic area may be formed in various ways, as by means of flanges on the cap pin, rings of metallic paint, or otherwise, and I have here illustrated merely one method, viz., by means of independent metallic rings 19 and 20. The ring 19 at its inner margin 21 is' upturned beneath the lower edge of the cap and enters the cement 15 by which it is held in position. The lower ring 20 is likewise upturned at its inner mar- "gin 22 and enters and is held in position by the cement surrounding the pin 18. i In like manner, but to less extent, the capacity of the insulators ingroup b is increased by means of 'the rings 23 and 2 1 Which are of less external diameter than those of the insulators in group a.

While these rings'increase the capacity (1 and C of each unit, they augment-particularly the internal capacity'C, as will be readily understood. Therings here shown may be stamped to shape, spun out of sheet metal'or otherwise formed. On account of the width'of the metal thus added to the insulator, it is'necessary to increase the diameter of the skirt 12 of the insulator in order "to secure a proper flash-over voltage.

A comparison between a string of ungraded insulators and a string of graded'i'ns'ulators is graphically illustrated in Figs. 6- and 7 respectively. The percentage of the total'voltage which is impressed upon"each insulator ofthe string is illustrated in terms of'th'a-t across the lineunit, which always shows the greatest voltage, 'curve'll Curve 2' gives the distribution of voltage along'the string in per cent. of the total-voltage. Each successive ordinate is obtained'by' adding the value of the 'per centof total voltage across that unit to the preceding ordinate. F or a perfectly uniform distribution of voltage this would be illustrated by a straight line (such as 3) from 1 to 15.

The result of grading the same type of unit illustrated in Fig. 6 is shown in Fig. 7.

Here the three'units next to the line have the largest conducting rings and a high internal capacity. The next five units are of somewhat smaller capacity, While the last seven units have normal capacity without alteration by means of the metal rings. Instead of uniform curves, the result is 'a broken line vention, and I do not limit thereto what I claim as my invention.

' I claim'as my invention 1. A multi-unit insulator, comprisin a plurality of insulator unitsof like type liut graded to predetermined different capacities increasing as the units approach the conductor carried 'by the insulator.

' 2'. A multi-unit insulator, comprising a plurality of groups of insulator units, the units of one group diifering in capacity vfrom the units of other groups, and increasing as the groups approach the conductor carried by the insulator. for the purpose specified.

3. A .inulti-unit insulator, comprising a plurality of groups of insulator units of like type, the units ofone group having a predetermined capacity different from the capacity of the units of another group, and

greater as the groups approach the conductor carried by the insulator, for the purpose described.

4. An insulator unit having metallic cap and pin, and an interposed insulating skirt, in combination with metallic bands respectively overlyin r and underlying said insulating ski'rt'an extending outward from the cap and pin areas of the insulator a less distance than, said insulating skirt, for the purpose described.

5'. 'An insulator unit having metallic cap and pin and an interposed insulating skirt, in combination with independent metal rings respectively overlying and underlyin said insulating skirt and extending outwar from thecap and pin' areas of the insulator a' less distance than said insulating skirt, for the purpose described.

overlying and underlying said insulating skirt and extending outward from the cap and pin areas of the insulator, the-extent of the metallic bands being greater in the units approaching the conductor carried by the insulator.

7. A multi-unit insulator, comprising a plurality of groups of insulator units each having a metallic cap and pin and interposed insulating skirt, and metallic bands respectively overlying and underlying said insulating skirt and extending outward from the cap and pin areas of the insulator, the extent of the metallic bands being constant for the insulators of each group but varying in different groups but being greater as the groups approach the conductor carried by the insulator, for the purpose described.

8. An insulator unit having cup-shaped head and outwardly extending flange or skirt integral therewith, metallic cap and pin respectively cemented upon and within said head, in combination with independent metallic rings overlying and underlying respectively said'skirt and embedded at their margins in the cement uniting the cap and pin to the insulator head.

9. A multi-unit insulator comprising a plurality of insulator units of the metallic cap and pin type, together with auxiliary metallic elements associated with at least some of said units to increase the normal capacity of those adjacent the conductor carried by the insulator.

10. A multi-unit insulator comprisin a plurality of insulator units of the meta lie cap and pin type, together with auxiliary metallic elements associated with at least some of said units to increase, by graduated steps, the normal capacity of those adjacent 1/ lator being greater than that of the units of a more remote group.

12. A multi-unit insulator comprising a plurality of groups of insulator units of the metallic cap and pin type, together with auxiliary metallic elements associated only with-those units approaching the conductor carried by the insulator and serving to increase the normal capacity of said units.

13. A multi-unit insulator comprising a plurality of interconnected insulator units and metal disks interposed between adjacent units toward the conductor-carrying end of the insulator for increasing the electrostatic capacity of the insulator units adjacent the conductor.

14. A multi-unit insulator comprising a plurality of interconnected insulator units and metallic disks of varying capacity interposed between adjacent units toward the conductor carrying end of the insulator for increasing the electrostatic capacity of the insulator units adjacent the conductor, the disks of greater capacity being nearer the conductor.

15. A multi-unit insulator comprising a plurality of interconnected insulator units and metallic disks varying in diameter interposed between adjacent units toward the conductor carrying end of the insulator for increasing the electrostatic capacity of the insulator units adjacent the conductor, the disks of greater diameter being nearer the conductor.

16. A multi-unit insulator comprising a plurality of interconnected. insulator units and conducting members interposed between said insulator units, said 'conductin members varying in capacity and'beingo greater capacity nearer the conductor carried by the insulator.

17. A multi-unit insulator comprising a plurality of interconnected insulator units and conducting members interposed between said insulator units, said conducting members varying in diameter, and those of greater diameter being nearer the conductor carried by the insulator. I

In testimony whereof I have signed my name to this specification, in the presence of two subscribing Witnesses.

RICHARD H. MARVIN; Witnesses:

ALMA M. WILLIAMS, H. S. RUssELL. 

